Sarah Mildred Long Bridge Replacement projectA photographic record

As usual, these photos are a couple of weeks old, but there are some interesting new developments to share. We'll start on the Kittery side. In the photo below, I'm standing on what will be the first shared road/rail pier, looking south along the alignment of the bridge. Remember that the trestle with the trucks and cranes is only temporary. The concrete piers that are starting to appear will carry the new bridge. Here, you can see in the foreground a cylindrical pier with a rectangular top, and another like it in the distance. These are the rail-only piers. The rail spans are half the length of the road spans (because of the weight they have to support), and have these intermediate piers between the shared piers. The workers in the center of the frame are working on the base of one of the shared piers. We'll get back to that in a minute.

Below is a view from above and to the left of the previous photo (taken from the sidewalk). It's a bit easier to see the layout of the piers in this one.

Let's take a look at the construction of that shared pier in the middle. Here's a closer look at what's going on. Workers are creating a cage of rebar that will form the base of the pier.

Jumping over to the Portsmouth side, we see one of these a bit further along. The base is complete, and rebar cages have been erected to form the two towers. In the distance in this photo, you can see one of the completed coffer dam piers. You'll notice that the one under construction has a much wider gap in the center. This is because it will accommodate the railroad down at the bottom, and the roadway at the top. The distant pier is beyond where the railroad will curve away from the bridge, and will only support the roadway.

Next, forms will be assembled around the rebar. Below we see the forms being prepared to be lifted into place. They are made up of the modular units seen stacked in the foreground. The white objects visible within the forms are styrofoam molds that give the piers their ornamental curved features.

Turning a little to the left, we see a worker polishing the inside surface of one of the form sections. This ensures a clean, smooth concrete surface and easy removal of the form when it has cured. The tubular structures are post tensioning ducts for the towers. They are upside down here. If you recall from the last post, the tower segments are stacked and then post tensioned (pulled together) with tendons (cables). These extend from the top of the tower to the base and are curved back upward by these ducts. This creates a mechanical advantage.

As I mentioned above, the rail line curves off of the bridge on both sides short of the road abutments. Below, you can see a cofferdam that has been erected at the location of the Portsmouth railroad abutment. The roadway will continue along the three cofferdam piers, and meet the existing road near the USS Albacore. At the left, you can see the rail line to Newington (originally Dover) from which it will diverge to head over the bridge. The switch will be in the vicinity of the point where it crosses under the existing bridge.

Both the road and railroad spans will be made of 6 foot segments that fit together a bit like legos (sideways), and are post-tensioned into complete spans. These segments are being cast in Pittsfield, MA, and rail span segments have started arriving by truck. The road span segments are too tall to truck, and will be shipped by rail in the fall. Below are two of the rail segments.

And finally, the tub. This large tub sits atop 8 drilled shafts and will serve as the base of the two Kittery towers. In the photo below, it has been set in place (it's made of several precast sections) and dewatered. You can see the rebar from the drilled shafts protruding. This whole thing will be filled with concrete. The two black pipes that are seen sticking up inside of the tub will carry electrical and data cables from the Portsmouth side, across the bottom of the river, to the Kittery side. The existing bridge gets power for the Portsmouth motor from NH and power for the Kittery motor from ME, which has been the source of some issues when one or the other stalls. The new bridge will get all of its power from the same source.In the final photo, you can see the 8 piers on the Portsmouth side waiting for their tub. Since I took these photos, the tub sections have arrived, and can be seen on barges awaiting installation.

Great job with photo's and explainations. I'm a civil engineer by training. I' impressed with progress and I live in York, ME. My poor view is from the high bridge each week so appreciate the close ups. Thanks.

Thank you so much for sharing all that information! Lived in Kittery for 30 yrs. I'm now almost 50 and have lived in Sanford, Me. For about 4yrs now. Don't get back down there much! Thanx so much as I've been curious. .

Reply

Nelson Linscott

7/18/2016 09:23:02 pm

Great site Eric. It is amazing the complexity of the rebar and the intricate shapes of the finished concrete especially the size they are. I remember the Sarah Long was a toll bridge with a ten or fifteen cent toll to cross. With no Rt 95 bridge at the time, you can imagine the traffic. The design of the old bridge was totally utilitarian being built in the 1940's and to me was an eyesore. This bridge looks to be a vast improvement.